Seam structures



Sept 8, 1959 M. MAESER ET AL SEAM STRUCTURES Original Filed June 30,

Inventors Nz'ef/z Maeser Frederick 15: Si/[czrs United States 1.,

SEA-M STRUCTURES 1 Mieth ;Maeser.and FrederickS. Sillars; Beverly, Mass.,

assigr ors to United Shoe Machinery Corporation, Flemmgton, N..I., a corporation of New Jersey Originalnapplication June 30, 1955, Serial No. 519,136. 7 Divided andthis applicatiomDecember 3,1956, Serial 2 Claims. (C31. 112-262) This invention relates to improvements in seams for uniting-two or 'morelayers ofworkby-adhesive fasten ings employed incombinationwith conventionally ar-. range,d-.thread.-

-'l"he.-subject matter hereintcontained has-already been disclosed in an application, for United States Letters Patent, Serial No.-5l9,l36, filedJune 30, 1955, in the names-of. the present-inventors,.of which application the presentone .is a division.

The above-identified parent application discloses a novel machine which may be utilized to insert charges of an. adhesive agent into the needleperforations of a thread scam in the work or alternatively to fasten multipledaiyers of work together solely by adhesive charges regularly spaced fromone another to format seam, the adhesive charges in either case being injected into the work athigh velocity.

In order to extend the, utility of threadseams for unit-- ing workpieces and to overcome some. of their inherent deficiencies, it hasbecome common practice in recent years to'employ a'fluid adhesive agentto form cement forbonding-the thread of conventional seams to thework being operated upon. To be effective, however, cemented seams must -provide improved bonding of: the thread to the, work while avoiding objectionable results characteristic to the :presence of the cement. Such objectionable results-appear when an adhesive agent "is applied to the thread exposed between the needle perforations of theseam, either when the thread is fully coated with an adhesive agent at the time that the stitches are formed or when the adhesive agent is deposited on the :exposed thread only. lneither case the formation .of hardened cementon anexposed surface objectionably stiffens the workin the area of the seamyand increases-the possibility ofrnarring or-otherwise spoiling the; appearance of the work by surplus deposits of. the adhesive agent: Such surplusdeposits of cement,- moreover may interfere with subsequent operations often'necessaryfor finishing the sewnv article. In addition, when the' thread is fully covered withanadhesive agent, difficulties are experienced in tightening the stitchesand further, the adhesive agent may be thrown off against the work-feedingand stitch-forming devices of the sewing machine and. interfere with their satisfactory operation.

In order, to avoid the difficulties .caused by thepresence of a liquid adhesive agent on exposed work surfaces, one expedient has been to insert adhesive plugs in semi-solid statewithin-the needle perforations; Such a seam'is dis closed in United StatesLetters .Patent, No. 2,486,531; granted-November. 1, .1949, upon application of Clyde L. Knott. The patented seamstructure isparticularly useful for attaching outsoles of shoes and for uniting layers of other relatively thick work. When properly inserted such seams provide a firm bond between the loops of thread and the work. Because the location of the plugs in the work and hence the quality of the seam depend on a variety of interacting factors, their satisfactory insertion requires care and close attention of a. highly Patented Sept. 8, 1959 ice in addition, the character, size, shape, and plasticity of' the plugs at the time of their insertion into the work. Any appreciable variation in one factor requires an accurate compensating adjustment inone or more of the others by a skilled operator.

It is an object of our invention to provide seam structures combining thread and a fluid adhesive agent which may be successfully inserted in work pieces by an operator having no greater skill than is necessary for forming uncemented seams. Another object is to provide anadhesive bonded lock stitch seam passingthrough multilayer work pieces through relatively long perforations of a diameter less than the combined thicknesses of the layers. A further object is to provide a cemented thread seam in'which insertion of the thread may be regulated independently of the cementing operation. Still another object is to provide a cemented thread seam in which there is a maximum area of'bond between the work and thread without the-necessity of having surplus deposits of cement formed on exposed work surfaces. Another object is to provide a seam structure for uniting multiple layer work and a barrier against the entry of moisture between the layers, both in a single operation. Another object is to waterproof the fibers of thread contained in the needle perforations of a conventional thread seam to prevent-deterioration of the thread.

In the achievement of the foregoing objects a principal feature of our invention resides ina seam structure inserted in-one or more layers of work in a conventional manner through perforations intersecting an interface of the layers and formed at least in part of adhesive agent hardened into cement within the perforations with con- I nections between the layers.

The adhesive agent is conveniently introduced into the perforations as a series of separate charges for reinforcing a continuous thread seam, one charge being introduced in each perforation and joined with each other between the layers by the apparatus of the above-identified parent application. By means of this apparatus a charge of adhesive agent is injected at high velocity into each needle perforation, completely impregnating the thread therein and anchoring the thread firmly to the work by an enlargement within the perforation at the interface between the layers. The size of the enlargement may be regulated to form ajun'ction with the charges in adjacent perforations thereby provid ing a continuous seal the entire length of the seam at the interface, it such is desirable in'a given work piece, to

exclude moisture or other foreign matter. The adhesive agent, preferably thermoplastic, thoroughly coats the fibers .of the thread not only improving their strength characteristics but also making them impervious to moisture which would otherwise cause premature deterioration.

The. foregoing objects, features, and advantages of our invention will be more fully understood from a description of an illustrative embodiment of the invention taken in connection with the accompanying drawo for a slightly modified seam structure.

Referring more particularly to Fig. 1 of the drawings,

a form of seam embodying the present invention is therein illustrated. The work operated upon is composed of multiple superimposed work layers, shown for the sake of simplicity as consisting of two parts 4 and 6, comprising the sole and welt respectively of a shoe. The stitches are inserted by the usual devices including an awl 8 and a needle 10 acting to form a series of perforations passing through the work layers 4 and 6 and to carry through the perforations and across an outer surface of the work successively loops of a continuous length of machine or needle thread 12. A similar continuous length of locking thread 14 is inserted into and inter locked with each projecting loop of needle thread to form a conventional lock stitch scam, the points of in,

terlocking engagement between the threads being located approximately half way between the surfaces of the outsole 4. After each stitch is formed and tightened to bring the point of interlocking engagement of the threads into the outsole, a charge of high velocity, hot melt liquid adhesive agent is injected into the stitch perforation.

The adhesive injecting apparatus, more fully described in the above-identified parent application, includes in addition to an impeller which meters and propels the adhesive charges, a special presser foot 16 having a nozzle 18 in communication through an internal passage 20 in the presser foot with the lower end of a flexible tube 22. The upper end of the tube 22 is connected to the impeller. The presser foot cooperates with a Work support 24 of conventional design for gripping and feeding the work. The nozzle 18 is positioned in registration with a needle perforation two stitches beyond the point of needle operation. The impeller is provided with separate adjusting means for changing the velocity of delivery and volume of the charge, more fully disclosed in the parent application, which charge is injected into the needle perforation in line with the nozzle 18.

The velocity and quantity of adhesive charge may be so determined that it continues in motion by its own inertia through each perforation in the outsole 4 to an interface 26 between the outsole and welt, the forepart of the charge being carried slightly beyond the point where the threads 12 and 14 are interlocked and the interface between the layers. As the velocity of charge is reduced by the resistance offered in filtering through the interstices of the thread it loses a substantial quantity of its heat especially along the area of the advancing front at the forepart of the charge. The reduction in velocity and solidifying action suddenly becomes critical and a dam 28 of cement is formed having a more or less solid convex area behind which the remainder of the adhesive charge builds up. Deeper penetration of the adhesive may be obtained on a given work piece by an increase in the velocity of injection. The advancing adhesive charge bringing with it the remainder of the heat initially contained therein, exerts a pressure on the solid darn 28 especially along the sides of a perforation, whereupon a portion of the charge spreads out to a substantial degree and migrates along the adjacent interface of the layers formed by the outsole and the welt. The quantity of the charge and the temperature to which it is raised may be so adjusted that the pressure on the sides of the perforation causes the charge to migrate more than half way from the perforation between the layers toward the adjacent charge, as shown in Fig. 1, thus forming a conjunction with the previous charge or the pressure may be insufficient to form a conjunction, as in Fig. 2.

Although the completed seam constructed in this way appears similar in all respects to: one having no adhesive reinforcement, it possesses far greater strength and durability. The velocity with which the adhesive agent is carried into the perforation is suflicient to prevent any external accumulation at the surface of the work piece through which the adhesive enters and the dam 28 forms a barrier for stopping the penetration of adhesive charge short of the other surface. Since the work layers are firmly pressed together at the point of adhesive injection by the tightened thread stitches the enlargement at the interface is limited to a thin section between the layers, the enlargement being of minimum thickness at the edge most remote from the perforation through which the adhesive agent is injected. Such a thin section of adhe sive agent forming cement under the heavy pressure of the stitches yields a bond between the layers which is far stronger than would be obtained without the benefit of the pressure. Another advantage of the thin section of cement is that the improved strength characteristic of the seam is obtained without appreciable loss of flexibility in the work. Greater durability of the seam is obtained by distributing a high velocity of adhesive charge throughout the length of each perforation filling any voids between the thread and the work and securely bonding the thread to the sides of the performation. Such distribution of the adhesive renders the thread impervious to moisture and prevents relative movement between the parts, two causes of premature failure in uncemented seams.

The nature and scope of the invention having been indicated and a particular embodiment having been de scribed, what is claimed is:

1. A thread seam uniting layers of dense and resistive work, such as leather shoe parts having, between outer faces of the work, a series of perforations each of a diam eter less than the combined thicknesses of the layers, and a continuous lockstitch having interlocking loops within the perforations and having lengths of thread passing from one perforation to another across the outer surface and in engagement with the work, the loop locks being positioned between the said faces, in combination with a discrete charge of hardened cement in each perforation entirely between the outer surfaces of the work, anchored to the work by a substantial enlargement of the cement at an interface between layers, and bonded to a substantial part of the thread within the perforation.

2. A thread seam uniting layers of dense and resistive layers of work, such as leather shoe parts, having, between outer faces of the work, a series of perforations each of a diameter less than the combined thicknesses of the layers and a continuous lockstitch having interlocking loops within the perforations and having lengths of thread passing from one perforation to another across the outer surface and in engagement with the work, the loop locks being positioned between the said faces, in combination with a discrete charge of solidified thermo plastic adhesive in each perforation entirely between the outer surfaces of the work, anchored to the work by a substantial enlargement of the cement at an interface between the layers, and bonded to the thread within the perforation.

References Cited in the file of this patent UNITED STATES PATENTS 2,020,300 Cnndall Nov. 12, 1935 2,189,067 Hlavaty Feb. 6, 1940 2,295,631 Boyer Sept. 15, 1942 FOREIGN PATENTS 649,390 Germany Aug. 21, 1937 

